1. Field of the Invention
The present invention relates to a fluorescent substance and a light emitting device using the fluorescent substance, and more particularly, to a fluorescent substance having significantly improved luminous intensity and a light emitting device using the fluorescent substance.
This application is based upon and claims the benefit of priority from Japanese patent application No. 2007-79406, filed on Mar. 26, 2007, the disclosure of which is incorporated herein in its entirely by reference.
2. Description of the Related Art
Various chalcopyrite type compounds are known as isoelectronic compounds with group IV elements. For example, II-VI type compounds and III-V type compounds having zinc blende crystal structure of groups II-VI, III-V and the like are cited. Each of them is composed of two kinds of elements which are opposite side of IV group elements and equidistant from IV group elements in the element periodic table. Further I-III-VI2 type compounds, II-IV-V2 type compounds and the like having copper pyrite crystal structures of I-III-VI2 group, II-IV-V2 group and the like are cited. Each of them is isoelectronic compound with II-VI compounds or III-V compounds. Of I-III-VI2 type compounds and II-IV-V2 type compounds, CuAlS2, CuGaS2 and the like have wide band gaps, and therefore, development of them are proceeding as light emitting materials of solar batteries, light emitting diodes, electroluminescence (EL), and the like.
More specifically, a thin film solar battery (Japanese Patent Laid-Open No. 9-181345) including a metallic electrode layer stacked on an insulating base in contact, a p-type chalcopyrite CuIn(x)Ga(1-x)Se2 semiconductor layer stacked in contact with the metallic electrode layer, a gradient composition layer stacked in contact with the p-type chalcopyrite CuIn(x)Ga(1-x)Se2 semiconductor layer, and a transparent electrode layer stacked in contact with the gradient composition layer is reported.
Further, there is reported a dispersed electroluminescence element (Japanese Patent Laid-Open No. 8-64361) or the like comprising a dielectric layer printed on a back electrode and a light emitting layer printed on the dielectric layer, in which the dielectric layer and the light emitting layer are sandwiched by the back electrode and a transparent conductive film. The light emitting layer is formed by using a printing material containing a dispersion as major proportions obtained by dispersing fluorescent substance powder, in which Mn as a luminescence center material is mixed and doped in CuAlS2, into a certain organic binder, so that red luminescence can be obtained.
However in the dispersed electroluminescence element disclosed in Japanese Patent Laid-Open No. 8-64361, the fluorescent substance contains Mn doped in CuAlS2 as the luminescence center material and various elements such as La, Ce and Pr as further materials, but chalcopyrite type compound containing silicon is never used as photoluminescence.
Further, display devices (Japanese Patent Laid-Open No. 6-89075) including an ultraviolet source which emits ultraviolet light in a plane form, a projection lens placed in a path of the ultraviolet light emitted from the ultraviolet source, and a fluorescent screen including a fluorescent substance layer containing a visible light-emitting fluorescent substance irradiated by the ultraviolet light, and the like are reported. However, in the display device disclosed in Japanese Patent Laid-Open No. 6-89075, CuAlS2 is used only for obtaining the photoluminescence effect of the chalcopyrite type compound or manganese chalcopyrite type compound.